Various systems for bone fracture fixation exist. Fractures of long bones may be treated by fixing an osteosynthesis plate on the bone bridging the fracture site. Alternatively, intramedular nails may be used.
Especially in the vicinity of a joint, such as shoulder, knee, elbow etc., high forces act on the bone. This is mainly caused by muscles and ligaments adhering to the bone in these areas. It is therefore especially important to provide fixation means which are strong enough to withstand the high forces and which offer good stability against distortion.
For fixation of fractures in the region of the proximal humerus there are various plate systems on the market. A few examples are the PHILOS plate (Synthes Inc., West Chester, Pa., USA), the AxSOS plate (Stryker Corp., Kalamazoo, Mich., USA) or the PERI-LOC proximal humerus locking plate (Smith & Nephew PLC., London, UK).
Fractures of the proximal humerus account for up to 4-5% of total fractures in humans. It is therefore a very frequent type of injury. As the muscles of the shoulder joint exert dragging forces on the fracture, dislocation of the fragments often occurs.
Further, there are many solutions directed to plates and osteosynthesis systems for fracture fixation on long bones in the area of joints. US 2003/0040748 describes a blade plate including a base portion and a blade portion. The blade portion is extending from the base portion at an angle and is inserted into the bone. A strut screw is insertable in a hole of the base portion such as to span the angle between the base and the blade portion.
Although this osteosynthesis system offers good stability against distortion of the plate, the insertion of the blade portion into the bone is complicated, since a cavity has to be reamed into the bone before the plate can be placed and secured by screws. Further, the strut screw spanning the fracture site does not offer stability against distortion, but rather serves to interlock and tension the blade and base portions. Also, due to the relatively bulky shape of the plate, this system may not be implanted with a minimal invasive surgery technique.
WO 2009/042783 describes a system for fracture fixation using a combination of an intramedullary nail and a small plate. Plate and nail are connected together through a spiral blade which is insertable through an opening in the plate into the bone and an opening of the nail.
DE 37 22 852 discloses a system comprising a first part in form of a plate to be positioned on the bone, a second part which may be inserted into bone as well as a truss screw which is insertable under an angle into the first plate part and which connects this part with the second part in the bone.
This system allows transforming bending forces, which may cause breakage of the plate, into dragging forces which are more readily absorbed by the components of the system. However, it does not provide for the prevention of distortion of the plate or the fracture.